1. Field of the Invention
The present invention relates to a clamper magnetism test method, and in particular to a method of clamper magnetism testing for a tray-type optical drive.
2. Description of the Related Art
The rapid development of optical media technology has resulted in the use of a variety of different optical drives as computer peripherals. The prevailing design trend is toward optical drives with high retrieval rate.
Optical drives can be categorized as either tray-type or slot-in type according to the way the optical disc is inserted. FIG. 1a shows a conventional tray-type optical drive, which has a tray 10, an optical pickup 20, a turntable 30, and one motor 40. The optical pickup 20, the turntable 30, and the motor 40 are disposed in a frame 50, and the tray 10 is movable and can be inserted into or ejected from the frame 50. Further, a supporting plate 26 is disposed in the frame 50 to hold the optical pickup 20 and the turntable 30.
The motor 40 drives the optical pickup 20, the turntable 30, and a transmission device 52, i.e. a plurality of gears and pulleys, on the frame 50. Generally, there is more than one motor 40 to drive the optical pickup 20, the turntable 30, and the transmission device 52 respectively. The tray 10 has a disc-receiving recess 12 for holding the optical disc and a rack (not shown) disposed under the tray 10 to engage the transmission device 52. Since the supporting plate 26 holds the optical pickup 20 and the turntable 30, the optical pickup 20 moves across the optical disc and the turntable 30 is inserted into the center hole of the optical disc to rotate the optical disc.
Further, a position detecting device, which includes an inner limit switch 54 and an outer limit switch 56 in FIG. 1a, is provided on the frame 50 for detecting and controlling the position of the tray 10 in relation to the frame 50.
Moreover, a clamping device, i.e. a clamper, is generally applied in the optical drive to secure the optical disc on the turntable 30 during rotation. FIG. 1b shows an example of the clamper in a conventional optical drive, in which the clamper 60 is disposed in a rocker shaft to rotate by the pivot 62. When an optical disc 1 is disposed in the optical drive and the turntable 30 is inserted into the center hole of the optical disc 1, the clamper 60 clamps the optical disc 1 on the turntable 30. Thus, the optical disc 1 held between the turntable 30 and the clamper 60 can rotate stably. The clamper 60 can be elastic, magnetic or another type of clamper.
When an optical disc 1 is to be loaded in the optical drive, the tray 10 is ejected. Generally, an ejection key on the panel of the optical drive is pressed 3 to eject the tray 10 from the optical drive. The optical disc 1 is then placed in the disc-receiving recess 12, on the tray 10. The tray 10 is then inserted into the optical drive. The turntable 30 then moves into the center hole of the optical disc 1 and the clamper 60 secures the optical disc 1 on the turntable 30 to rotate the optical disc 1. The optical pickup 20 then moves across the optical disc 1 to perform read and write operations.
Generally, a direct current (DC) motor is employed as the motor 40 to drive and control the sliding of the tray 10 and the clamping operation of the clamper 60. The output torque and the power of the DC motor are variable depending on the input voltage. Thus, ejection or insertion of the tray 10 and the clamping motion of the clamper 60 can be performed simultaneously, and the operation of the optical drive can be effectively enhanced.
The ejection of the tray 10 and the clamping motion of the clamper 60 are described in detail with reference to the flowchart shown in FIG. 1c. When the ejection key on the panel of the optical drive is pressed, an ejection command is sent to the optical drive (step S10), and an input voltage is provided to the DC motor 40 to simultaneously drive the clamper 60 and the transmission device 52 (step S20). Thus, a preliminary ejection stage of the tray 10 is initiated, in which the clamper 60 releases the optical disc 1, and the transmission device 52 provides an ejecting force to the tray 10 over a preliminary time period. When the tray 10 starts moving and activates the inner limit switch 54, the preliminary ejection is completed (step S30), and the optical disc 1 moves off the reading position.
Since the clamper 60 should be disengaged from the optical disc after preliminary ejection, the DC motor 40 stops providing voltage to the clamper 60 and continue driving the transmission device 52 to completely eject only the tray 10 (step S40). The outer limit switch 56 (step S50) is activated during ejection of the tray 10, indicating that ejection is complete, thereafter, the DC motor 40 stops powering the transmission device 52 (step S60).
When the clamper 60 of the tray-type optical drive is a magnetic clamper, however, the magnetic force of the magnetic clamper 60 may be weak or abnormal due to manufacturing flaws or other defects. In this case, reading or writing errors may occur, and the optical disc 1 may be damaged during operation due to inconsistent clamping force.
Preferably a plurality of magnetism tests are performed on each magnetic clamper 60 prior to assembly. However, It wastes a lot of time doing tests on every clamper, and also abnormal magnetic force due to manufacturing flaws and defects, or operation, can hardly be detected prior to assembly.